Polypeptide multilayer films on colloidal particles: an in situ electro-optical study

The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on beta-FeOOH colloidal particles was investigated by means of electro-optics and electrophoresis. The films were built at different (acidic) pH in the absence of salt. We found that the thickness of the film grows linearly when the fully charged PLL (at pH 5.5) is combined with almost fully charged PGA (at pH 6.5), with a thickness of about 2 nm per single layer. When the fully charged PLL is combined with weakly charged PGA (at pH 4.5), the film thickness increases exponentially with the number of deposited layers. The thickness of the exponentially growing film increases to 300 nm after deposition of 16 layers. The exponential film growth is attributed to the ability of the PLL to diffuse "in" and "out" of the film bulk at each deposition step. The variation in the electrical polarizability of the film-coated particles was also monitored as a function of the number of adsorbed layers. The result reveals that the PLL chains, which can diffuse into the film bulk, have no measurable contribution to the electro-optical effect of the films terminated with PLL. It is only due to the polarization of counterions of the PLL adsorbed on the film surface.     

Stability of polypeptide multilayers as studied by in situ ellipsometry: effects of drying and post-buildup changes in temperature and pH

Polyelectrolyte multilayers (PEM) of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) with an initial layer of polyethyleneimine (PEI) were built on silica and titanium surfaces using the layer-by-layer (LbL) technique. The stability of the film during drying/rewetting, temperature cycles, and pH shifts was studied in situ by means of ellipsometry. The film thickness was found to decrease significantly (approximately 70%) upon drying, but the original film thickness was regained upon rewetting, and the buildup could be continued. The thickness in the dry state was found to be extremely sensitive to ambient humidity, needing several hours to equilibrate. Changes in temperature and pH were also found to influence the multilayer thickness, leading to swelling and deswelling of as much as 8% and 10-20% respectively. The film does not necessarily regain its original thickness as the pH is shifted back, but instead shows clear signs of hysteresis.     

Influence of the polyelectrolyte molecular weight on exponentially growing multilayer films in the linear regime

Alternated deposition of polyanions and polycations on a charged solid substrate leads to the buildup of polyelectrolyte multilayer (PEM) films. Two types of PEM films were reported in the literature: films whose thickness increases linearly and films whose thickness increases exponentially with the number of deposition steps. However, it was recently found that, for exponentially growing films, the exponential increase of the film thickness takes place only during the initially deposited pairs of layers and is then followed by a linear increase. In this study, we investigate the growth process of hyaluronic acid/poly(L-lysine) (HA/PLL) and poly(L-glutamic acid)/poly(allylamine) (PGA/PAH) films, two films whose growth is initially exponential, when the growth process enters the linear regime. We focus, in particular, on the influence of the molecular weight (Mw) of the polyelectrolytes. For both systems, we find that the film thickness increment per polyanion/polycation deposition step in the linear growth regime is fairly independent of the molecular weights of the polyelectrolytes. We also find that when the (HA/PLL)n films are constructed with low molecular weight PLL, these chains can diffuse into the entire film during each buildup cycle, even for very thick films, whereas the PLL diffusion of high molecular weight chains is restricted to the upper part of the film. Our results lead to refinement of the buildup mechanism model, introduced previously for the exponentially growing films, which is based on the existence of three zones over the entire film thickness. The mechanism no longer needs all the "in" and "out" diffusing polyanions or polycations to be involved in the buildup process to explain the linear growth regime but merely relies on the interaction between the polyelectrolytes with an upper zone of the film. This zone is constituted of polyanion/polycation complexes which are "loosely bound" and rich in the polyelectrolyte deposited during the former deposition step.     

Reinvestigation on the buildup mechanism of alternate multilayers consisting of poly(L-glutamic acid) and poly(L-, D-, and DL-lysines)

The buildup mechanism of polypeptide multilayers prepared by the layer-by-layer deposition of a polyanion (poly(L-glutamic acid) (PGA)) and polycations (poly(L-lysine) (PLL), poly(D-lysine) (PDL), and copoly(DL-lysine)(PDLL)) was reinvestigated by using in situ ATR-IR spectroscopy. A difference spectral technique applied to analyze the spectra indicated that the deposition of both the PGA and PLL (PDL) layers accompanies the formation of secondary structures consisting mainly of the antiparallel pleated sheet (the beta-sheet) structure, and that the formation of the beta-sheet structure cannot always be explained in terms of polyanion/polycation complex formation or charge compensation between the polyanion and polycations, although it has been considered as a major process in the multilayer buildup process. Instead, the present paper proposes the following mechanism. During the deposition of the polyelectrolyte, a small amount of the beta-sheet structures are produced at the interface as a result of charge compensation between a polyelectrolyte and an oppositely charged polyelectrolyte in the multilayer. The beta-sheets act as nuclei from which further propagation of the structure takes place at the solution/multilayer interfaces. The driving force of the buildup process in the new mechanism is a kinetically favorable insolubilization of each polyelectrolyte in solution at the interfaces.     

Characteristics of polyelectrolyte multilayers: effect of PEI anchoring layer and posttreatment after deposition

The influence of a first (anchoring) layer and film treatment on the structure and properties of polyelectrolyte multilayer (PEM) films obtained from polyallylamine hydrochloride (PAH) and polysodium 4-styrenesulfonate (PSS) was studied. Branched polyethyleneimine (PEI) was used as an anchoring layer. The film thickness was measured by ellipsometry. Complementary X-ray reflectometry and AFM experiments were performed to study the change in the interfacial roughness. We found that the thickness of the PEM films increased linearly with the number of layers and depended on the presence of an anchoring PEI layer. Thicker films were obtained for multilayers having PEI as the first layer comparing to films having the same number of layers but consisting of PAH/PSS only. We investigated the wettability of PEM surfaces using direct image analysis of the shape of sessile water drops. Periodic oscillations in contact angle were observed. PAH-terminated films were more hydrophobic than films with PSS as the outermost layer. The effect of long time conditioning of PEM films in solutions of various pH's or salt (NaCl) concentrations was also examined. Salt or base solutions induced modification in wetting properties of the polyelectrolyte multilayers but had a negligible effect on the film thickness.     

Partial poly(glutamic acid) <--> poly(aspartic acid) exchange in layer-by-layer polyelectrolyte films. Structural alterations in the three-component architectures

Layer-by-layer (LBL) polyelectrolyte films were constructed from poly(L-glutamic acid) (PGA) and poly(L-aspartic acid) (PAA) as polyanions, and from poly(L-lysine) (PLL) as the polycation. The terminating layer of the films was always PLL. According to attenuated total reflection Fourier transform infrared measurements, the PGA/PLL and PAA/PLL films, despite their chemical similarity, had largely different secondary structures. Extended beta-sheets dominated the PGA/PLL films, while alpha-helices and intramolecular beta-sheets dominated the PAA/PLL films. The secondary structure of the polyelectrolyte film affected the adsorption of human serum albumin (HSA) as well. HSA preserved its native secondary structure on the PGA/PLL film, but it became largely deformed on PAA/PLL films. Both PGA and PAA were able to extrude to a certain extent the other polyanion from the films, but the structural consequences were different. Adding PAA to a (PGA/PLL)5-PGA film resulted in a simple exchange and incorporation: PGA/PLL and PAA/PLL complexes coexisted with their unaltered secondary structures in the mixed film. The incorporation of PGA into a (PAA/PLL)5-PAA film was up to 50% and caused additional beta-structure increase in the secondary structure of the film. The proportions of the two polyanions were roughly the same on the surfaces and in the interiors of the films, indicating practically free diffusion for both polyanions. The abundance of PAA/PLL and PGA/PLL domains on the film surfaces was monitored by the analysis of the amide I region of the infrared spectrum of a reporter molecule, HSA, adsorbed onto the three-component polyelectrolyte films.     

In situ layer-by-layer film formation kinetics under an applied voltage measured by optical waveguide lightmode spectroscopy

Layer-by-layer (LbL) thin film assembly occurs via the alternate adsorption of positively and negatively charged macromolecular species. We investigate here the control of LbL film growth through the electric potential of the underlying substrate. We employ optical waveguide lightmode spectroscopy (OWLS) to obtain in situ kinetic measurements of poly(allylamine hydrochloride)/poly(sodium 4-styrenesulfonate) (PAH/PSS) and poly(L-lysine)/dextran sulfate (PLL/DXS) multilayer film formation in the presence of an applied voltage difference (deltaV) between the adsorbing substrate, an indium tin oxide- (ITO-) coated waveguiding sensor chip, and a parallel platinum counterelectrode. We find initial layer adsorption to be significantly enhanced by an applied potential for both polyelectrolyte systems: the mass and thickness of (positively charged) PAH and PLL layers on ITO are about 60% and 500% larger, respectively, at deltaV = 2 V than at open circuit potential (OCP), in apparent violation of electrostatics. A kinetic analysis reveals the initial attachment rate constant to decrease with voltage, in agreement with electrostatics. To reconcile these results, we propose a more coiled and loosely bound adsorbed polymer conformation at higher applied potential. Following 10 adsorption steps, the mass and thickness of a PAH/PSS film grown under deltaV = 2 V are about 15% less than those of a comparable film grown under OCP, reflecting a lower degree of complexation between adsorbing polyanions and more highly coiled adsorbed polycations. Following 14 adsorption steps, the mass and thickness of a PLL/DXS film grown under deltaV = 2 V are about 70% greater than those of a comparable film grown under OCP, reflecting the increased charge overcompensation in the initial layer. We find the scaling of film mass () with the number of adsorption steps (n) to be linear in the PAH/PSS system and exponential (i.e., approximately eyn) in the PLL/DXS system, irrespective of applied voltage. We observe to decrease with applied voltage and to exhibit a crossover to a smaller value around n = 5. Extrapolation reveals PLL/DXS multilayer films to be suppressed by increased voltage in the limit of large n: the mass of films grown at OCP and deltaV = 1 V would surpass that of a film grown under deltaV = 2 V at about the 23rd and 18th adsorption steps, respectively. The formation kinetics of PLL/DXS, but not PAH/PSS, change qualitatively under voltage: PLL adsorption is slow to reach a plateau, possibly due to the formation of secondary structure, and a decrease in film mass occurs toward the end of each DXS adsorption step, suggesting spontaneous removal of some PLL/DXS complexes from the film.     

Hydrophobically modified polyelectrolyte for improved oxygen barrier in nanobrick wall multilayer thin films

The influence of attaching hydrophobic side groups to a polyelectrolyte, used for deposition of a multilayer oxygen gas barrier thin film, was investigated. Polyethyleneimine (PEI) was labeled with pyrene and deposited in “quadlayers” of PEI, poly(acrylic acid), PEI, and sodium montmorillonite clay using layer‐by‐layer assembly. Thin films made of three repeating quadlayers using unmodified PEI had much lower density (1.24 g/cm³) than pyrene‐labeled PEI‐based films (1.45 g/cm³), which is believed to be the result of greater chain coiling from the increased hydrophobicity of pendant pyrene groups. This increased density in pyrene‐labeled PEI layers allowed three quadlayers to match the oxygen transmission rate of a four quadlayer film made with unmodified PEI. This discovery provides an additional tool for tailoring the barrier behavior of clay‐based multilayer thin films that could prove useful for a variety of packaging applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1153–1156     

Human serum albumin self-assembly on weak polyelectrolyte multilayer films structurally modified by pH changes

Adsorption of proteins onto film surfaces built up layer by layer from oppositely charged polyelectrolytes is a complex phenomenon, governed by electrostatic forces, hydrogen bonds, and hydrophobic interactions. The amounts of the interacting charges, however, both in polyelectrolytes and in proteins adsorbed on such films are a function of the pH of the solution. In addition, the number and the accessibility of free charges in proteins depend on the secondary structure of the protein. The subtle interplay of all these factors determines the adsorption of the proteins onto the polyelectrolyte film surfaces. We investigated the effect of these parameters for polyelectrolyte films built up from weak "protein-like" polyelectrolytes (i.e., polypeptides), poly(L-lysine) (PLL), and poly(glutamic acid) (PGA) and for the adsorption of human serum albumin (HSA) onto these films in the pH range 3.0-10.5. It was found that the buildup of the polyelectrolyte films is not a simple function of the pure charges of the individual polyelectrolytes, as estimated from their respective pKa values. The adsorption of HSA onto (PLL/PGA)n films depended strongly on the polyelectrolyte terminating the film. For PLL-terminated polyelectrolyte films, at low pH, repulsion, as expected, is limiting the adsorption of HSA (having net positive charge below pH 4.6) since PLL is also positively charged here. At high pH values, an unexpected HSA uptake was found on the PGA-ending films, even when both PGA and HSA were negatively charged. It is suggested that the higher surface rugosity and the decrease of the alpha-helix content at basic pH values (making accessible certain charged groups of the protein for interactions with the polyelectrolyte film) could explain this behavior.     

Metal-enhanced fluorescence using silver nanoparticles-embedded polyelectrolyte multilayer films for microarray-based immunoassays

Metal-enhanced fluorescence (MEF) of quantum dots (QDs) and its potential application in microarray-based immunoassays was investigated using silver nanoparticles (AgNPs) prepared by the in situ photoreduction of Ag⁺ inside a multilayer film consisting of poly(ethyleneimine) (PEI) and hyaluronic acid (HA). UV–Vis spectroscopy, X-ray diffraction, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy confirmed the formation of well-dispersed AgNPs within the multilayer films, the thickness and the amount of which depended on the number of HA layers. Using AgNPs-containing hybrid multilayered films, it was possible to observe the MEF effect of adsorbed QDs, which could be tuned by the thickness of interlayer spacer film prepared of the layer-by-layer assembly of PEI and poly(styrene sulfonate). When the MEF-inducing hybrid film was used as a platform for immunoassay, a significant improvement in the fluorescence signal and sensitivity of the biosensing were observed in the presence of AgNPs in comparison with films that did not contain the nanoparticles.     

Immobilization of enamel matrix derivate protein onto polypeptide multilayers. Comparative in situ measurements using ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry

The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.     

Assembly of poly(N-isopropylacrylamide)-co-acrylic acid microgel thin films on polyelectrolyte multilayers: Effects of polyelectrolyte layer thickness, surface charge, and microgel solution pH

Temperature- and pH-sensitive poly(N-isopropylacrylamide)?Cco-acrylic acid (pNIPAm-co-AAc) microgels were deposited on glass substrates coated with polyelectrolyte multilayers composed of the polycation poly(allylamine hydrochloride) (PAH) and the polyanion poly(sodium 4-styrenesulfonate) (PSS). The microgel density and structure of the resultant films were investigated as a function of: (1) the number of PAH/PSS layers (layer thickness); (2) the charge on the outer layer of the polyelectrolyte multilayer film; and (3) the pH of microgel deposition solution. The resultant films were studied by differential interference contrast optical microscopy, atomic force microscopy, and scanning electron microscopy. It was found that the coverage of the microgels on the surface was a complex function of the pH of the deposition solution, the charge on the outer layer of the polyelectrolyte thin film and the PAH/PSS layer thickness; although it appears that microgel charge plays the biggest role in determining the resultant surface coverage.     

Stimulation and binding properties of polyelectrolyte multilayers verified by ATR‐FTIR spectroscopy

We report on the deposition and properties of multilayers composed of reactive polymers on planar surfaces. As reactive polymers the poly cations poly(ethylene‐imine), poly(L‐lysine) (PLL), poly(allylamime) (PAA) and the polyanions poly(acrylate) (PAC), poly(vinylsulfate), poly(maleate‐co‐olefines) were used. ATR‐FTIR Spectroscopy was adopted to study deposition, binding and stimulation properties of polymer multilayers. The binding of charged species of different molecular size such as rhodanide anions and sodium oleate from solution was examined, whereby binding was found to be dependent on the charge of the outermost layer. For these two analytes a selectivity parameter Q, defined as the ratio between the adsorbed amount obtained at the negatively charged and that at the positively charged surface, respectively, was determined. Furthermore, swelling experiments on multilayer assemblies of PLL and PAC exposed to mixtures of ethanol/water (10–70% EtOH content) were carried out. Our experiments gave evidence, that the PLL layers showed a more significant increase in density than the PAC layers. The conformation of PLL incorporated into multilayers could be changed by pH variation.     

Stabilization of protein-loaded starch microgel by polyelectrolytes

The interaction of biocompatible polyelectrolytes (chargeable poly(amino acids)) with oxidized starch microgel particles has been studied. The aim was to form a polyelectrolyte complex layer around the outer shell of microgel particles filled with functional ingredients to slow down the release of the ingredients from the gel and make this process less sensitive to salt. First, the distribution of positively charged poly(l-lysine) (PLL) of two different molecular weights ("small", 15-30 kDa, and "large", 30-70 kDa) in the negatively charged gel particles was measured. The small PLL distributes homogeneously throughout the gel particles, but the large PLL forms a shell; i.e., its concentration at the outer layer of the particles was found to be much higher than in their core. This shell formation does not occur at a relatively high salt concentration (0.07 M). The large PLL was selected for further study. It was found that upon addition of PLL to lysozyme-loaded gel particles the protein is exchanged by PLL. The exchange rate increases with increasing pH, in line with the increasing electrostatic attraction between the gel and the polyelectrolyte. Therefore, it was decided to use also a negatively charged poly(amino acid), poly(L-glutamic acid) (PGA), to form together with PLL a stable polyelectrolyte complex shell around the gel particles. This approach turned out to be successful, and the PLL/PGA complex layer effectively slows down the release of lysozyme from the microgel particles at 0.05 M salt. In addition, it was found that the PLL/PGA layer protects the gel particle from degradation by α-amylase.     

Influence of assembling pH on the stability of poly(L-glutamic acid) and poly(L-lysine) multilayers against urea treatment

Polyelectrolyte multilayers of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) were built up using the layer-by-layer (LbL) technique in low pH (3.6, PM3.6) and in neutral pH (7.4, PM7.4) solutions. The multilayers were then treated with a concentrated urea (one kind of denaturant for proteins and polypeptides) solution (8M) and rinsed with corresponding buffer. The buildup and treatment processes were investigated by ultraviolet visible spectroscopy and ellipsometry. The surface morphology was observed by scanning force microscopy (SFM). The inner structures were determined by X-ray reflectometry and circular dichroism spectroscopy (CD). An exponential growth of the optical mass and the layer thickness was observed for both PM3.6 and PM7.4. After urea treatment, a significant mass loss for PM3.6 was found, while no mass change was recorded for PM7.4. The dominant driving force for PM7.4 is electrostatic interaction, resulting in multilayers with an abundant beta-sheet structure, which has higher stability against urea treatment. By contrast, the dominant driving force for PM3.6 is hydrogen bonding and hydrophobic interaction, which are sensitive to the urea treatment. The mechanism is substantiated by molecular mechanics calculation. This has offered a convenient pathway to mediate the multilayer properties, which is of great importance for potential applications.     

Polyelectrolyte multilayers and degradable polymer layers as multicompartment films

Polyelectrolyte multilayers are now a well established concept with numerous potential applications in particular as biomaterial coatings. To timely control the biological activity of cells in contact with a substrate, multicompartment films made of different polyelectrolyte multilayers deposited sequentially on the solid substrate constitute a promising new approach. In a first paper (Langmuir 2004, 20, 7298) we showed that such multicompartment films can be designed by alternating exponentially growing polyelectrolyte multilayers acting as reservoirs and linearly growing ones acting as barriers. In the present study, we first demonstrate however that these barriers composed of synthetic polyelectrolytes are not degraded despite the presence of phagocytic cells. We propose an alternative approach where exponentially growing poly(L-lysine)/hyaluronic acid (PLL/HA) multilayers, used as reservoirs, are alternated with biodegradable polymer layers consisting in poly(lactic-co-glycolic acid) (PLGA) and acting as barriers for PLL chains that diffuse within the PLL/HA reservoirs. We first show that these PLGA layers can be deposited alternatively with PLL/HA multilayers leading to polyelectrolyte multilayer/hydrolyzable polymeric layer films and acting as a reservoirs/barriers system. Bone marrow cells seeded on these films ending by a PLL/HA reservoir rapidly degrade it and internalize the PLL chains confined in this reservoir. Then the cells degraded locally the PLGA barrier and internalize the PLL localized in a lower (PLL/HA) compartment after 5 days of seeding. By changing the thickness of the PLGA layer, we hope to be able to tune the time delay of degradation. Such mixed architectures made of polyelectrolyte multilayers and hydrolyzable polymeric layers could act as coatings allowing us to induce a time scheduled cascade of biological activities. We are currently working on the use of comparable films with compartments filled by proteins or peptides and in which the degradation of the barriers results from a hydrolysis over tunable time scales.     

Dipping versus spraying: exploring the deposition conditions for speeding up layer-by-layer assembly

Polyelectrolyte film fabrication by successive spraying of polycation and polyanion solutions is described and compared to classic dipping. The poly(styrenesulfonate)/poly(allylamine) system is examined in detail. The influence of various parameters such as spraying time, polyelectrolyte concentration, and effect of film drying during multilayer construction is investigated. It is found that film deposition by spraying is easily controlled and very reliable. The thickness of the multilayers grows linearly with the number of deposition cycles similarly to what is observed when dipping substrates or when polyelectrolyte solutions flow over a surface. The assembly of films is very fast and leads to films with small surface roughness as estimated by atomic force microscopy and X-ray reflectometry. Spray deposition allows achieving regular multilayer growth even under conditions for which dipping fails to produce homogeneous films (e.g., extremely short contact times). Moreover, because drainage constantly removes a certain quantity of the excess material arriving at the surface, one can even skip the rinsing step and, thus, speed up even further the whole buildup process.     

The electroactive multilayer films of polyelectrolytes and Prussian blue nanoparticles and their application for H2O2 sensors

Prussian blue (PB) nanoparticles were immobilized in polyelectrolyte (PE) multilayers of various compositions and thickness. Films containing nanoparticles and poly(allylamine hydrochloride) (PAH) were formed using the layer-by-layer adsorption method. A layer of branched poly(ethyleneimine) (PEI) was used to anchor the multilayer structure at the surface of a gold electrode. The films exhibited electroactive properties, increasing with the number of deposited PB layers. The properties of PEI/(PB/PAH) _n multilayers were then compared with the ones containing additionally the conductive polymer poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS). We found that the addition of the conductive, water-soluble polymer enhances the electroactive properties of the multilayer films. It also increased sensitivity of the multilayer-covered electrodes for electrochemical detection of hydrogen peroxide.     

Construction of Polycation‐Based Non‐Viral DNA Nanoparticles and Polyanion Multilayers via Layer‐by‐Layer Self‐Assembly

Summary: The multilayers of polycation‐based non‐viral DNA nanoparticles and biodegradable poly(L ‐glutamic acid) (PGA) were constructed by a layer‐by‐layer (LbL) technique. Poly(ethyleneimine) (PEI) was used to condense DNA to develop non‐viral DNA nanoparticles. AFM, UV‐visible spectrometry, and TEM measurements revealed that the PEI‐DNA nanoparticles were successfully incorporated into the multilayers. The well‐structured, easily processed multilayers with the non‐viral DNA nanoparticles may provide a novel approach to precisely control the delivery of DNA, which may have great potential for gene therapy applications in tissue engineering, medical implants, etc.

A TEM image of the cross section of a (PGA/PEI‐DNA nanoparticle)₂₀ multilayer.     

Enhancement of surface wettability via the modification of microtextured titanium implant surfaces with polyelectrolytes

Micrometer- and submicrometer-scale surface roughness enhances osteoblast differentiation on titanium (Ti) substrates and increases bone-to-implant contact in vivo. However, the low surface wettability induced by surface roughness can retard initial interactions with the physiological environment. We examined chemical modifications of Ti surfaces [pretreated (PT), R(a) ≤ 0.3 μm; sand blasted/acid etched (SLA), R(a) ≥ 3.0 μm] in order to modify surface hydrophilicity. We designed coating layers of polyelectrolytes that did not alter the surface microstructure but increased surface ionic character, including chitosan (CHI), poly(L-glutamic acid) (PGA), and poly(L-lysine) (PLL). Ti disks were cleaned and sterilized. Surface chemical composition, roughness, wettability, and morphology of surfaces before and after polyelectrolyte coating were examined by X-ray photoelectron spectroscopy (XPS), contact mode profilometry, contact angle measurement, and scanning electron microscopy (SEM). High-resolution XPS spectra data validated the formation of polyelectrolyte layers on top of the Ti surface. The surface coverage of the polyelectrolyte adsorbed on Ti surfaces was evaluated with the pertinent SEM images and XPS peak intensity as a function of polyelectrolyte adsorption time on the Ti surface. PLL was coated in a uniform thin layer on the PT surface. CHI and PGA were coated evenly on PT, albeit in an incomplete monolayer. CHI, PGA, and PLL were coated on the SLA surface with complete coverage. The selected polyelectrolytes enhanced surface wettability without modifying surface roughness. These chemically modified surfaces on implant devices can contribute to the enhancement of osteoblast differentiation.